Research on the effects of mood on judgment and evaluation has found that mood exerts a mood-consistent bias, by (a) making mood-consistent concepts more available in memory when interpreting information, (b) informing the direction of an evaluative judgment, and (c) biasing recall of information in a mood-consistent manner. When applied to models of behavior over time, mood is thought to operate as a cognitive positive feedback system. For instance, depressives are likely to make negative interpretations which cycle back into a more depressed state. this implies that breaking out of a negative mood would be quite difficult. Preliminary research, however, has found evidence for mood improvement over time under certain conditions of interpersonal interaction. Specifically, interacting with someone in a presumed similar mood state, even if that mood is negative, seems to improve mood, while dissimilarity in presumed mood state seems to inhibit mood improvement. Preliminary research also indicates a contrast effect in judgment of others' mood, rather than a mood-consistent bias, that may prevent this perception of similarity. The primary objective of this program of research, then, is to begin to develop and refine a model of mood and interaction based on mood similarity that can explain and predict changes in mood over time. three studies are proposed that attempt to identify the salient features of such a model. These studies look at factors such as actual vs. perceived mood similarity and nonverbal features of interaction (in particular, nonverbal synchrony) that may mediate the similarity effect. An understanding of the mechanisms of mood improvement in interaction is important, since interpersonal interaction is the primary context for most of daily living. Furthermore, some methods of mood improvement include destructive behaviors such as alcohol consumption and drug use. Given the obvious mental health and social implications, it is important to research more effective and less harmful strategies of mood management.